> terrifying implications of pure bloodlines that are very much with us today

Funny, I've never heard of these from any folkie or read about them on any LP jacket. Quite the contrary in fact.

Yet, because I know the world of tenure-track academia, I understand these presumed "terrifying implications" are quite "unconscious" and therefore don't require any objective evidence of their existence.

But what about Nazis?

The Nazi use of genuine folksongs as sound-track says nothing about the songs. Lots about the craftiness of Nazis, though.